Molecular dynamics simulation of despentapeptide insulin in a crystalline environment

Despentapeptide insulin (DPI), an analogue of insulin, is the only analogue of insulin existing as a monomer in crystalline form so far discovered. A 31 picosecond molecular dynamics simulation of DPI was carried out in the unit cell that includes four DPI molecules, 398 water molecules, four Cd2+, eight Na+ and four Cl-. The molecular dynamics results were compared with the available X-ray structure in terms of atomic positions, backbone dihedral angles, hydrogen bonds and positional fluctuations. Good agreement was found between the molecular dynamics results and the X-ray data. The largest root-mean-square fluctuations were observed at the N-terminal part of the B chain. This fits with the experimental observation.